Detection of Wet Condition for Underwater Local Dry Welding

摘要

Local dry underwater welding is one of the key technologies for on site construction and maintenance of very large offshore floating structures(Mega-Float). Mechanical properties for wet welding is relatively poor compared to dry welding because of bad influence by surrounding water at the welding part. Local dry welding procedure by using of water curtain shield is one solution to improve mechanical properties. This technique is so simple to reduce much cost and working time, if complete dry condition is guaranteed during welding operation. This paper describes a way to visualize two-dimensional wet condition using an infrared video camera with an optical bandpass filter for automatic detection of water on a plate to be welded. The water has absorption spectra in the infrared region at wave lengths 1450nm and 1940nm. An IR sensitive video camera (from 500 to 2000nm) combined with an optical bandpass filter (1450nm) was used to visualize the wet condition on steel plate. Wet region was recognized automatically by image processing.